1. Field of the Invention
The described invention relates to the field of optical circuits. In particular, the invention relates to thermal compensation in an optical waveguide.
2. Description of Related Art
Optical circuits include, but are not limited to, light sources, detectors and/or waveguides that provide such functions as splitting, coupling, combining, multiplexing, demultiplexing, and switching. Planar lightwave circuits (PLCs) are optical circuits that are manufactured and operate in the plane of a wafer. PLC technology is advantageous because it can be used to form many different types of optical devices, such as array waveguide grating (AWG) filters, optical add/drop (de)multiplexers, optical switches, monolithic, as well as hybrid opto-electronic integrated devices. Such devices formed with optical fibers would typically be much larger or would not be feasible at all. Further, PLC structures may be mass produced on a silicon wafer.
PLCs often have been based on silica-on-silicon (SOS) technology, but may alternatively be implemented using other technologies such as, but not limited to, silicon-on-insulator (SOI), polymer on silicon, and so forth.
Thermal compensation for some optical circuits, such as phase-sensitive optical circuits, is important as devices may be operated in locations where temperatures cannot be assured. In some cases, optical circuits are combined with temperature regulating equipment. However, these configurations may be less than ideal, since the devices are prone to failure if there is a power outage, and temperature regulating equipment may require a large amount of power which may not be desirable.